The largest source of death is miscarriage, or spontaneous abortion. Indeed, if one considers a
fertilized egg an “equally valuable” human life with “full human
rights,” then spontaneous miscarriage is the single leading cause of
death for "fully-valuable human beings". And that includes if you are also going to say that life begins at implantation.

That would mean that God causes the most abortions if you are looking at this from a theological viewpoint ratter than a scientific one. In fact, perhaps we should go with the medical term "spontaneous abortion" rather than "miscarriage".

If we did that, would women who have miscarriages be guilty of aborting their foeti? Even if we go beyond conception, we also have miscarriages up until birth and still-births.

The question is then "when does a foetus become viable"?

In a secular society, which is what the United States happens to be, it really isn't the place of religion to dictate that type of decision. In fact, it is is properly a decision which should be made by a women informed by her physician: not the state.

And definitely not religion.

Especially if god happens to be the worst culprit for causing abortions.

Aditionally, you also have to admit that one needs to provide proper pre-natal care if you are going to take the attitude that the pre-born have some right to life. Unfortunately, most of the ideologically pro-lifers hate "Obamacare", let alone a single payer system of health care.

In fact, I find the ideologically "pro-life" tend to be lost on the actual concept of all this.